Compressor unloading means



July 19, 1966 E. J. KOCHER 3,261,541

COMPRESSOR UNLOADING MEANS Filed Nov. 29. 1963 2 Sheets-Sheet 1 COMPRESSOR SUCT'ON DISCHARGE 2/ 22 INVENTOR. ERICH J. KOCHER m & meew Affonwevs July 19, 1966 E. J. KOCHER 3,261,541

COMPRESSOR UNLOADING MEANS Filed Nov. 29, 1963 2 Sheets-Sheet 2 v ii INVENTOR. ERICH J. KOCHER ATTORNEYS pressor discharge.

United States Patent O 3,261,541 COMPRESSOR UNLOADING MEANS Erich J. Kocher, Milwaukee, Wis., assignor to Vilter Manufacturing Corporation, Milwaukee, Wis., 21 corporation of Wisconsin Filed Nov. 29, 1963, Ser. No. 326,946 7 Claims. (Cl. 230-31) This invention relates to compressors and the control of compressors, and more particularly to a means for controlling compressor capacity under loaded and unloaded conditions.

It is the primary object of this invention to provide an automatic compressor capacity control which is responsive to fluid pressure at the compressor discharge.

Compressor unloader controldevices are found in the .prior art as exemplified, for example, in US. Patents No. 2,626,099, No. 2,673,025, and No. 2,869,775. In Patent No. 2,626,099, the unloading mechanism is actuated by means of a power element which in turn is actuated by oil pressure. In Patent No. 2,673,025, the unloading mechanism and its control are energized by the lubrication system of the compressor. In Patent No. 2,869,775, a partition is provided in the compressor together with valve means for separating the lubricant and the foam while permitting oil to return to the crankcase.

None of these prior art patents utilize the expedient means of controlling the unloading of a compressor by means of the high pressure refrigerant gas from the com- The unloader control mechanism of the present invention provides for automatic compressor capacity control and permits the compressor to start in an unloaded condition. While loading and unloading is actuated by compressor suction pressure variations, the

unloading control mechanism is actuated by the high pressure refrigerant gas from the compressor to move a control piston to various positions to thereby regulate the oil supply to the compressor cylinder unloaders in an efficient manner. When there is no oil pressure in the compressor, the cylinder unloaders hold the suction valve open thereby allowing the cylinders to operate in an unloaded condition. When oil pressure is generated as by a pump or the like, the cylinder unloaders permit the suction valves to function normally, and the compressor cylinders then operate at full capacity. Thus, the compressor will always start and operate with the cylinders in an unloaded condition until sufficient oil pressure is obtained to actuate the cylinder unloaders.

It is therefore another object of the invention to provide an improved unloader control system for a compressor wherein the compressor cylinders may be unloaded by holding the suction valve of each cylinder open thereby permitting easy and ready starting of the compressor, and to enable variations in the capacity of the compressor cylinders in response to changes in load condition.

A further object of this invention is to provide a capacity control for a compressor wherein cylinder unload- 3,261,541 Patented July 19, 1966 ing is actuated in response to compressor discharge pressure and compressor suction pressure.

Another object of the invention is to provide an improved unloader control for a compressor which allows a compressor to operate at maximum capacity.

A further object of the invention is to provide means to control the operation of the compressor in accordance with compressor discharge pressure.

These and other objects and advantages of the invention will become apparent from the following detailed description:

A clear conception of the several features constituting the present invention and the mode of operation in a typical reciprocating compressor embodying the improvements may be had by referring to the drawings accompanying and forming a part of this specification, wherein like reference characters designate the same or similar parts in the various views:

FIGURE 1 is a schematic in perspective of a refrigeration system;

FIGURE 2 is an enlarged elevational view in section of the compressor of FIGURE 1 embodying the invention;

FIGURE 3 is an enlarged elevational view in section of the compressor unloader control device of FIGURE 2, shown as subjected to a first compressor condition;

FIGURE 4 is a view of the unloader device similar to FIGURE 3 wherein a second compressor condition is shown; and

FIGURE 5 is a view of the unloader device similar to FIGURE 3 wherein a third compressor condition is shown.

Referring now to FIGURE 1 wherein a refrigeration system 10 is shown having a compressor 11 for dischargdriven by an electric motor (not shown) or by other suitable power means. The compressor may have any desired number of'cylinders and any suitable arrangement of cylinders. The cylinders arrangements are old and well known in the art and do not constitute a part of this invention.

Reference is now made to FIGURE 2 wherein the compressor 11 is shown provided with a main housing 20'having a suction inlet21 and a compressor discharge outlet 22 with cylinders 23 and 24 interposed therebetween for the compression of refrigerant gas ina manner well known in the art.

A crank shaft 25 is rotatably driven by power shaft 26 to cause reciprocal action of piston means 27 and 28. An oil pump 29 is powered by the rotation of crank shaft 25 to pump :oil from thelower portion of crankcase 30 via conduit 29a to a discharge conduit 2% to lubricate;

. bellows 45.

the compressor and to power the unloading of the cylinders 23, 24 as described in greater detail hereinafter.

Also shown in compressor housing 20 is an unloader piston control device 31 provided with oil delivery conduits 32, 33, 34, and 35 for actuating cylinder unloader piston means 31a. An unloader piston control valve means 36 is located in a bore 37 and is adapted to be positioned longitudinally therealong by pressure in chamber 40-acting at piston surface 38 against the force of spring 39. Compressor discharge gas pressure is communicated to the chamber 40 immediately adjacent piston surface 38 by a conduit 41 having a metering orifice 42 therein. The gas pressure in chamber 40 is regulated by the relative position of a valve member 43 in relation to a conduit 44 to determine the amount of discharge gas that will flow exterior of a bellows 45. Interior of bellows 45 is a compression spring 46 that is adjustable as by a .screw 47; The exterior of bellows 45 within bellows housing 45a is in communication with compressor suction pressure in chamber 48 by a gas conduit 49.

The unloader piston control device 31 reacts to variations in suction pressure existing in chamber 48 via conduit 49. The suction pressure in chamber 48 determines the position of valve member 43 to regulate the pressure in chamber 40 which is supplied with high pressure refrigerant gas from the compressor discharge through conduit 41 and orifice 42. The position of valve member 43 is changed from a closed to an open position upon'an increase in suction pressure through conduit 49. The valve member 43 returns to a closed position when the suction pressure in conduit 49 and chamber 45a drops. This suction pressure is balanced against atmospheric pressure entering through conduit 50 as biased by spring 46 and As hereinabove described, the amount of tension in spring 46 is adjustable as by screw 47.

When the refrigeration system requires less than full load capacity from the compressor 11, the suction pressure in suction chamber 48 will fall below a predetermined value, and the drop in suction pressure will be communicated via conduit 49 to bellows chamber 45a resulting in a positioning of valve member 43 toward conduit 44. With valve member 43 closing or nearly closing conduit 44, the gas pressure in chamber 40 will increase to position unloader control valve piston 36 against the pressure of spring 39. As piston 36 is positioned longitudinally along bore 37 toward spring 39, an annular collar 51 of the piston is positioned first to allow oil conduit 34 to communicate with chamber 55 for discharge through port 35 to crankcase 30, and if piston 36 positioning continues t-oward spring 39, conduit 33 is also communicated to chamber 55 for discharge of oil through port 35.

Upon increases in the demands of the refrigerating system 10, the suction pressure in chamber 48 increases above a predetermined value to cause the valve member 43 to move away from conduit 44 to reduce the pressure in chamber 40, thereby allowing the spring 39 to return unloader piston 36 to the position shown in FIGURE 3.

inders 23, 24 are operating in an unloaded condition.

The unloader piston control device 31 further consists of an annularly grooved portion 52 wherein a chamber 53 is continuously connected to oil pump pressure through conduit 32. When the unloader control valve piston 36 is positioned as shown in FIGURE 3, the oil from chamber 53 is fed to the cylinder unloaders 31a through conduits 33 and 34 to thereby load the compressor cylinders 23 and 24. Upon a drop in suction pressure, the unloader control valve piston 36 is moved 4 t to the position shown in FIGURE 4 as occasioned by an increase in gas pressure in chamber 40 as hereinabove described, and the oil trapped in conduit 34 is released to the crankcase 30 through chamber 55 and port 35 thereby unloading cylinder 23 to balance the reduced compressor load.

If the suction pressure continues to decrease, the unloader control valve piston 36 continues to move against spring 39 to the position shown in FIGURE 5 to relieve the oil pressure from conduits 33 and 34 through chamber 55 and port 35 to the crankcase 30, thereby unloading the compressor cylinders 23, 24 to again balance the compressor load. Upon an increase in compressor load and subsequent increase of suction pressure at chamber 48, the unloader control valve piston 36 is again moved to the position shown in FIGURE 3 to load the compressor cylinders 23 and 24.

Thus, an unloader control valve device for a compressor has been described wherein an unloader control valve piston is positioned in response to compressor load as actuated by the high pressure discharge gas pressure and compressor suction gas pressure to provide an automatic compressor capacity control to permit the compressor to start in an unloaded condition so that the compressor cylinders are operable at full capacity, and to balance the compressor loading over a range of gas pressures.

Various modes of carrying out the invention are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.

I claim:

1. An unloading control system for a compressor having a suction chamber, a high pressure discharge, compression means, and unloading means therefor; said system comprising, a valve mounted on the compressor for controlling the unloading means, a source of oil pressure for the compressor, said control valve communicating with the unloading means and with said source of oil pressure, a conduit from the compressor discharge to said control valve for positioning said valve responsive to pressures existing in said conduit to thereby control the flow of oil under pressure from said source to the unloadingmeans, and means actuated by compressor suction pressure for selectively relieving and permitting pressure build-up in said conduit dependent on the conditions prevailing in the suctionchamber.

2. The system of claim 1, wherein the control valve includes a reciprocable piston having spring means acting on one end thereof to constantly resiliently urge the same toward a position wherein the unloading means is inefiective, the opposite end of said piston being exposed to the conduit communicating with the pressure discharge.

3. The system of claim 1, wherein the control valve includes a pressure chamber communicating with the conduit from the compressor discharge, and the means which is actuated by compressor suction pressure regulates the pressure in said pressure chamber whereby the pressure in said pressure chamber acts on said control valve to position the same.

4. Thesystem of claim 2, wherein a pressure chamber is provided at the end of the piston communicating with the compressor discharge, and the means which is actuated by compressor suction pressure varies the pressure in said pressure chamber in response to pressure conditions prevailing'at said suction chamber for positioning said control valve piston against the action of the spring means in accordance with pressure variations in said pressure chamber.

5. The system of claim 4, wherein the means which is actuated by the compressor suction pressure is a pilot valve which relieves pressure in the pressure chamber whenever the suction pressure reaches a predetermined operating condition to thereby permit the control valve piston to assume a normal position under action of the spring means.

6. The system of claim 1, wherein the means whic 2,462,039 2/1949 Gibson 23031 is actuated by the compressor suction pressure includes 2,626,099 1/1953 Ashley 230-25 a bellows resiliently biased toward a position permitting 2,638,265 5/1953 Newton 230-31 pressure build-up in the conduit from the compressor dis- 2,836,345 5/ 1958 Gerteis 23031 charge to the control valve. 5 2,917,225 12/1959 Hanson et a1. 230-31 7. The system of claim 6,, wherein means is provided 2,991,924 7/1961 Ramsay 230-30 for adjusting the degree of resilient biasing of the bellows. 3,040,969 6/ 1962 Nicholas et a1. 230-31 FOREIGN PATENTS References Cited by the Examiner 10 939,587 10/ 1963 Great Britain.

UNITED STATES PATENTS 1,598,637 9/ 1926 Bayles 23031 MARK NEWMAN, Primary Examiner.

1,917,316 7/1933 Naab 230-31 2,185,473 1/1940 Neeson 23o 31 DONLEY STOCKING Examme" 2,387,117 10/1945 Buehler 230-30 15 W. I. KRAUSS, Assistant Examiner. 

1. AN UNLOADING CONTROL SYSTEM FOR A COMPRESSOR HAVING A SUCTION CHAMBER, A HIGH PRESSURE DISCHARGE, COMPRESSION MEANS, AND UNLOADING MEANS THEREOF; SAID SYSTEM COMPRISING, A VALVE MOUNTED ON THE COMPRESSOR FOR CONTROLLING THE UNLOADING MEANS, A SOURCE OF OIL PRESSURE FOR THE COMPRESSOR, SAID CONTROL VALVE COMMUNICATING WITH THE UNLOADING MEANS AND WITH SAID SOURCE OF OIL PRESSURE, A CONDUIT FROM THE COMPRESSOR DISCHARGE OR SAID CONTROL VALVE FOR POSITIONING SAID VALVE RESPONSIVE TO PRESSURES EXISTING IN SAID CONDUIT TO THEREBY CONTROL THE FLOWOF OIL UNDER PRESSURE FROM SAID SOURCE TO THE UNLOADING MEANS, AND MEANS ACTUATED BY COMPRESSOR SUCTION PRESSURE FOR SELECTIVELY RELIEVING AND PREMITTING PRESSURE BUILD-UP IN SAID CONDUIT DEPENDENT ON THE CONDITIONS PREVAILING IN THE SUCTION CHAMBER. 